Benzodiazepine derivatives are useful compounds for treating various disorders, and include medicaments such as, antiepileptics (imidazo[2,1-b][1,3,5]benzothiadiazepines, U.S. Pat. No. 4,444,688; U.S. Pat. No. 4,062,852), antibacterials (pyrimido[1,2-c][1,3,5]benzothiadiazepines, GB 1476684), diuretics and hypotensives (pyrrolo(1,2-b)[1,2,5]benzothiadiazepine 5,5 dioxide, U.S. Pat. No. 3,506,646), hypolipidemics (WO 03091232), anti-depressants (U.S. Pat. No. 3,453,266); osteoporosis (JP 2138272).
Recently, it has been shown in animal tumor models that benzodiazepine derivatives, such as pyrrolobenzodiazepines (PBDs), act as anti-tumor agents (N-2-imidazolyl alkyl substituted 1,2,5-benzothiadiazepine-1,1-dioxide, U.S. Pat. No. 6,156,746), benzo-pyrido or dipyrido thiadiazepine (WO 2004/069843), pyrrolo[1,2-b][1,2,5]benzothiadiazepines and pyrrolo[1,2-b][1,2,5]benzodiazepine derivatives (WO2007/015280), tomaymycin derivatives (e.g., pyrrolo[1,4]benzodiazepines), such as those described in WO 00/12508, WO2005/085260, WO2007/085930, and EP 2019104. Benzodiazepines are also known to affect cell growth and differentiation (Kamal A., et al., Bioorg Med Chem. 2008 Aug. 15; 16(16):7804-10 (and references cited therein); Kumar R, Mini Rev Med Chem. 2003 June; 3(4):323-39 (and references cited therein); Bednarski J J, et al., 2004; Sutter A. P, et al., 2002; Blatt N B, et al., 2002), Kamal A. et al., Current Med. Chem., 2002; 2; 215-254, Wang J-J., J. Med. Chem., 2206; 49:1442-1449, Alley M. C. et al., Cancer Res. 2004; 64:6700-6706, Pepper C. J., Cancer Res 2004; 74:6750-6755, Thurston D. E. and Bose D. S., Chem Rev 1994; 94:433-465; and Tozuka, Z., et al., Journal of Antibiotics, (1983) 36; 1699-1708. General structure of PBDs is described in US Publication Number 20070072846. The PBDs differ in the number, type and position of substituents, in both their aromatic A rings and pyrrolo C rings, and in the degree of saturation of the C ring. Their ability to form an adduct in the minor groove and crosslink DNA enables them to interfere with DNA processing, hence their potential for use as antiproliferative agents.
The first pyrrolobenzodiazepine to enter the clinic, SJG-136 (NSC 694501) is a potent cytotoxic agent that causes DNA inter-strand crosslinks (S. G Gregson et al., 2001, J. Med. Chem., 44: 737-748; M. C. Alley et al., 2004, Cancer Res., 64: 6700-6706; J. A. Hartley et al., 2004, Cancer Res., 64: 6693-6699; C. Martin et al., 2005, Biochemistry., 44: 4135-4147; S. Arnould et al., 2006, Mol. Cancer Ther., 5: 1602-1509). Results from a Phase I clinical evaluation of SJG-136 revealed that this drug was toxic at extremely low doses (maximum tolerated dose of 45 μg/m2, and several adverse effects were noted, including vascular leak syndrome, peripheral edema, liver toxicity and fatigue. DNA damage was noted at all doses in circulating lymphocytes (D. Hochhauser et al., 2009, Clin. Cancer Res., 15: 2140-2147). Thus, there exists a need for improved benzodiazepine derivatives that are less toxic and still therapeutically active for treating a variety of proliferative disease states, such as cancer.